DESCRIPTION: The long-term goal is the elaboration and study of proteins containing synthetic amino acids at specific, predetermined positions and the kinetics of there enzyme reactions These are to be incorporated by read throug of nonsense codons with misacylated suppressor tRNAs. It is proposed to continue the preparation and study of analogs of E. coli dihydrofolate reductase, firefly luciferase and HIV-1 protease. Also proposed for study are methods that have the potential to increase the efficiency of synthesis of the analogs of interest, as well as the repertoire of amino acid analogs that can be incorporated.